Don't scrutinize its plot mechanics too closely and you might squeeze some enjoyment out of Hammer's Crescendo. A tame cousin to one of the studio's previous grand guignol entries, Die! Die! My Darling! (1965), this one is less powerful, but surprisingly ballsy and well acted.

Working on her thesis, music scholar Susan Roberts (Powers) pays a visit to the South of France in order to study the career of a recently deceased symphonic composer named Ryman. She's greeted at the idyllic family estate by the musician's widow Danielle (Scott) and her wheelchair-bound son Georges (Olson).

Susan's lovely, to be sure. She's also intelligent and fiercely determined, so she'd prefer to get right down to business researching Ryman's eccentric past.

Alas, Susan's studies won't be fruitful. Because something is afoot at the Ryman villa. George is besieged by violent seizures and terrible fits of anxiety. At night, strange music seems to emanate unexplainably from a locked ante room. Susan's belongings never seemed to arrive, and Danielle appears intent on Susan staying on, well, permanently. And what's with the Rymans' creepy French maid Lillianne (Lapotaire)?

To tell all would be unfair to the uninitiated. Suffice it to say Crescendo is a satisfying mix of grand guignol goodness and a worthy addition to Hammer's rabid cycle of post PSYCHO thrillers (such as Nightmare and Hysteria).

Competent direction from Alan Gibson (who helmed the psycho-twin thriller Goodbye Gemini the same year), and a restful, pastoral feel courtesy of cinematographer Paul Beeson, lay the foundation for much of Crescendo's creaky attic theatrics.

But it's Powers, Olson and Scott who build upon that foundation. Powers has never looked more beautiful than here. Although there are times when the kooky script gives her character less motivation than she deserves, she proves to be a trooper by delivering a believable performance as a beleaguered graduate student caught up in one family's high gothic dysfunction.

Kudos also to Olson...who seems to be having the most fun here as the troubled invalid Georges. The actor has a field day toying with the possibilities of his character: is Georges merely a man with a few serious problems? Or an out and out deranged lunatic?

Rounding up the trio is Margaretta Scott as the formidable matriarch Danielle Ryman. She's no match for Tallulah Bankhead in Die! Die! My Darling!, it's true. Nevertheless, Scott channels the best of a latter day Joan Bennett, and cuts a striking figure as a mature mother with a secret to hide...and danger behind her very smile.

During its finer moments - such as the scene where Susan discovers strange, broken female mannequins in the Rymans' music room - Crescendo holds its own against other Hammer thrillers of this mold, most notably the excellent Scream of Fear (1961).

Admittedly, there are some lowlights. The plot is too loosely woven and particularly near the end, things unravel to a questionable degree. The Rymans' brooding butler Carter (Ackland) is underused, and there's a faint whiff of the overly familiar about the whole thing.

Still, Hammer fans (and genre lovers) would do well by this superior-crafted potboiler which makes for a thrilling, toe-warming winter watch.